Thin films of ferroelectric materials and a method for preparing same

a technology of ferroelectric materials and thin films, which is applied in the direction of metallic material coating process, liquid/solution decomposition chemical coating, coating, etc., can solve the problems of inability to randomly orientated pzn-pt films with a very low pzn composition, and inability to achieve optimal characteristics of commercial applications. , to achieve the effect of high dielectric constant, excellent piezoelectric properties and strong ferrolectriqu

Active Publication Date: 2006-08-17
AGENCY FOR SCI TECH & RES
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  • Abstract
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  • Claims
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Benefits of technology

[0081] A further advantage of the present invention over the present technology is that the thickness of thin films of ferroelectric material could extend across the range from micrometers to nanometer, rather than being constrained to beyond several micrometers.
[0082] The thin films of ferroelectric materials of the present invention exhibit a high dielectric constant and excellent piezoelectric properties. For example, the thin film of 0.77(0.6PZN-0.4PMN)-0.23PT discussed in Example 5 exhibits strong ferrolectric characteristics. The dielectric constant and loss are 3497 ad 0.06 at 1 kHz, respectively, and the dilatation of the thin film is about 325 pm in thickness direction at 5V.
[0083] Accordingly, it is envisaged that the thin films of ferroelectric materials of the present invention will be employed in microelectronic devices and microelectromechanical systems (MEMS) devices, such as: (1) integrated piezoelectric micro-actuators for many diverse applications, including microfluidic, ink-jet printing, nano-positioning (for example for hard disk drive, nano-scale manipulation, and such like), micro ultrasonic devices, optical switchers and modulators, switchers for RF MEMS, actuators for bioMEMS; (2) high frequency ultrasonic transducers for medical imaging; (3) micro resonators for many device applications; (4) integrated piezoelectric sens...

Problems solved by technology

However, the preparation of useful perovskite PZN-based thin films is extremely challenging because of the poor stability of the perovskite phase relative to the pyrochlore phase for the PZN composition.
Furthermore, the perovskite crystallographic structure in the prepared films was not in a preferred orientation.
A randomly orientated PZN-PT film with a very low PZN composition does not demonstrate optimal characteristics for commercial applications for s...

Method used

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  • Thin films of ferroelectric materials and a method for preparing same

Examples

Experimental program
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Effect test

example 1

PZN-PT Thin Films on LAO Substrate

[0118] In this example, the preparation of epitaxial ferroelectric (1-x)Pb(Zn1 / 3Nb2 / 3)O3-xPbTiO3 (PZN-xPT) thin films on a perovskite LaAlO3 (LAO) single crystal substrate is described.

[0119] The PZN precursor solution was prepared by first dissolving zinc acetate trihydrate (0.00500 mol) in 2-methoxyethanol (2-MOE) at 80° C. Subsequently, niobium isopropoxide (0.01000 mol) was added to the solution with mechanical stirring or reluxing. The solution was allowed to clarify then cooled to room temperature. A separate solution of lead acetate trihydrate (0.01725 mol) in 2-MOE was prepared at 115° C. and the solution was stirred for 15 minutes. The two solutions were then mixed at room temperature and diluted with 2-MOE to obtain a concentration of 0.3 M.

[0120] The PT precursor solution was prepared by dissolving lead acetate trihydrate (0.03450 mol) in 2-MOE at 115° C. A separate solution of titanium isopropoxide (0.0300 mol) in 2-MOE was prepared a...

example 3

PZN-XPT Thin Films on Perovskite Conductive Oxide Layers on Silicon

[0143] Epitaxial PZN-XPT thin films can also be prepared on a conductive oxide layer which is expitaxially grown on some substrates whose structures or lattice parameters do not match perovskite PZN-xPT thin film through introduction of appropriate buffer layers. The perovskite conductive thin films include LaxSr1-xMnO3, LaxCa1-xFeO3, LaNiO3, SrRuO3, LaxSr1-xCoO3, LaxSr1-xFeO3, etc.

[0144] In Example 3, epitaxial yttria-stabilized zirconia (YSZ), YBa2Cu3o7-δ(YBCO), and La0.7Sr0.3MnO3 (LSMO) layers are successively grown on (100)-oriented single crystal silicon substrate, followed by deposition of an epitaxial PZN-xPT thin film. The epitaxial deposition of the conductive LSMO and its buffer layers can be achieved by using any existing methods of epitaxy and, notably, vapor phase epitaxy, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), metal organic molecular beam epitaxy (MOMBE) or liqu...

example 5

(1-x)Pb((Zn,Mg)⅓Nb⅔)03-xPbTiO3(PZMN-xPT) Thin Films on LSMO / LAO

[0159] An epitaxial La0.7Sr0.3MnO3 (LSMO) thin film was coated on a LAO substrate as bottom electrode by pulsed laser deposition (PLD) method. The processing conditions were the same as described in Example 3, resulting in a conductivity of about 3×10−4 Ω·cm.

[0160] A PZMN-xPT thin film was then coated using the same PZMN-PT solution with 60 wt % PEG200 additive, which was prepared according to the method in Example 4, on the top of the LSMO film. The spin coating was conducted at 5000 rpm for 30 seconds in a clean room. Each coating layer was dried at 100° C. for 2 minutes, followed by pyrolysis at 430° C. for 5 minutes and pre-annealing at 580° C. for 10 minutes. A thickness of 1 um was obtained by repeating the process. Finally, the film was annealed at 700° C. for 10 minutes.

[0161]FIG. 16 (a) and (b) show the XRD patterns of the 0.77(0.6PZN-0.4PMN)-0.23PT thin films grown on the LSMO-coated LAO substrates, annealed...

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Abstract

Thin films of ferroelectric material with a high mole fraction of Pb(A2+1/3B5+2/3)O3 substantially in a perovskite phase, wherein A is zinc or a combination of zinc and magnesium, and B is a valence 5 element such as niobium or tantalum, have been prepared. Typically, the mole fraction of Pb(A2+1/3B5+2/3)O3 in the ferroelectric material is >0.7. The method for preparing the thin films of ferroelectric material comprises providing a precursor solution containing lead, A2+, and B5+; modifying the precursor solution by addition of a polymer species thereto; applying the modified precursor solution to a surface of a substrate and forming a coating thereon; and (d) subjecting the coating to a heat treatment and forming the film in the perovskite phase. Optimal results have been obtained with PEG200 as the polymer species.

Description

FIELD OF THE INVENTION [0001] The present invention relates to thin films of a ferroelectric material and a method of preparation therefor. In particular the present invention relates to thin films of ferroelectric material with a high mole fraction of Pb(Zn1 / 3Nb2 / 3)O3 in a perovskite phase. BACKGROUND OF THE INVENTION [0002] In recent years, perovskite oxide solid-solution systems based on ferroelectric Pb(Zn1 / 3Nb2 / 3)O3 (PZN), such as (1-x)Pb(Zn1 / 3Nb2 / 3)O3-xPbTiO3 (PZN-PT); have attracted great attention due to their extremely large electromechanical strain and high dielectric constant. A PZN-PT single crystal exhibits high electromechanical coupling coefficients (k33>90%), and high piezoelectric coefficients (d33>2200 pC / N), properties which are significantly superior to those of the most widely used piezoelectric Pb(Zr,Ti)O3 (PZT) materials. Therefore, the success in developing perovskite PZN-PT bulk single crystal is thought as the most significant breakthrough in piezoele...

Claims

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Application Information

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IPC IPC(8): H01L21/00
CPCC23C18/1216C23C18/1241H01L41/1875H01L41/314H10N30/8548H10N30/078
Inventor YAO, KUIYU, SHUHUITAY, FRANCIS ENG HOCK
Owner AGENCY FOR SCI TECH & RES
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